In November of 1985, Kroto et al., (Nature 318, 162) disclosed the experimental evidence for the existence of a family of spherically shaped, carbon molecules which they dubbed "fullerenes". Since their discovery, there has been an extensive amount of research on this family of molecules and their uses such as superconductors, lubricants, chemical precursors, non-linear optical materials, diamond film seed layers and photosensitizers for refractive polymers.
Kroto et al. used laser beam vaporization of graphite to synthesize the fullerenes. Unfortunately, this method results in the formation of only small amounts of fullerene product.
In 1990, Kratschmer et al., Nature 347, 354 (1990) disclosed a method for the mass production of fullerenes involving resistive or arc heating of a dense graphite rod in an inert atmosphere. This method achieves a higher yield of the sixty carbon atom fullerenes. Diederich et al., "Beyond C.sub.60 : The Higher Fullerenes", Acc. Chem. Res. 25, 119 (1992) also discloses synthesizing fullerenes by resistive heating of a dense graphite rod. Diederich discloses that the yield of higher fullerenes having greater than seventy carbon atoms is relatively low. Such higher fullerenes arc particularly important as diamond film seed layers. Parker et al., "High Yield Synthesis, Extraction and Mass Spectrometric Characterization of Fullerenes C.sub.60 to C.sub.266 " JACS 113 7499 (1991) discloses organic extraction procedures for extracting a greater amount of higher fullerenes from the raw product formed by resistive heating of a dense graphite rod. However, while improved extraction procedures can increase the amount of recovery of higher fullerenes from the raw product, the amount of recovery is limited by the low yield of the higher fullerenes in the raw product.
Therefore, there still is a need in the art for a process which gives a higher yield of higher fullerenes having greater than seventy carbon atoms.
It is therefore an object of the present invention to provide an improved process for the production of higher fullerenes having greater than seventy carbon atoms.
Other objects and advantages will become apparent from the following disclosure.